The role of infectious agents in the pathogenesis of reversible obstructive airway disease (asthma) is at present undefined. This project is designed to examine this relationship in children by a series of related clinical and laboratory studies. The developmental role of respiratory virus infection in asthma is being examined; by means of a long-term prospective study we are examining the prognosis of acute bronchiolitis in infants, with particular reference to the subsequent development of asthma. We are extending our own previous studies in order to better define the role of respiratory viruses in exacerbations of wheezing in asthmatic children. The mechanism by which virus infection leads to wheezing in children is also being explored. A rational basis for the use of liver respiratory vaccines is being examined in a series of studies on the role of secretory antibody in defense against natural respiratory viral infection, and the immunogenic and protective effect of experimental attenuated respiratory viral vaccines. We are also conducting studies of the antibody status of infants and children before and after bronchiolitis in the first year of life caused by specific viral agents. Finally, we are investigating the role of coronaviruses in lower respiratory disease of infants and children.